This relates generally to imaging systems, and more particularly, to imaging systems with through-oxide vias (TOVs).
Modern electronic devices such as cellular telephones, cameras, and computers often use digital image sensors. Imaging systems (i.e., image sensors) often include a two-dimensional array of image sensing pixels. Each pixel typically includes a photosensitive element such as a photodiode that receives incident photons (light) and converts the photons into electrical signals. The imaging system contains an image sensor die with an image sensor integrated circuit and an array of photodiodes. The image sensor die is mounted on a digital signal processor (DSP) die.
Circuitry within the image sensor die may be coupled to circuitry within the digital signal processor die using through-oxide vias (i.e., metal via structures formed through at least a first oxide layer in the image sensor die and through at least a second oxide layer in the DSP die). A bond pad is subsequently formed on the image sensor die. The bond pad may be coupled to the through-oxide vias. A first passivation layer is formed over the bond pad to passivate the bond pad. This passivation layer is then opened to allow wirebonding. After the passivation layer is opened an array of color filter elements is formed on the image sensor die. An array of microlenses is then formed over the array of color filter elements.
A second passivation layer is formed over the array of microlenses. This passivation layer acts as an anti-reflective coating over the microlenses. This passivation layer is subsequently opened over the bond pad to allow wirebonding. Forming image sensor dies in this way requires a large number of steps and can be costly.
It would therefore be desirable to provide improved ways of manufacturing image sensor dies.